Drosophila sonorae Heed and Castrezana

Heed, William B. & Castrezana, Sergio, 2008, Drosophila sonorae (Diptera, Drosophilidae), a new species in the repleta species group from Mexico, Zootaxa 1725, pp. 27-36 : 28-32

Drosophila sonorae Heed and Castrezana sp. nov.

Figures 1 a–b, 2a–b, 3a–b

Diagnosis. Drosophila sonorae is closely related to and sympatric with D. longicornis in Navojoa , Sonora. Drosophila sonorae can be differentiated from D. longicornis by the lateral pattern in the abdomen. The lateral areas in tergite 4th and 5th of Drosophila sonorae are completely cover by a prolongation of the apical band while in the tergites 1st to 3rd the apical band is clearly separated from the marginal band (figure 2b). On the other hand, in D. longicornis the apical band in all tergites had a transparent or “smooth” connection with the lateral margin and it varies in intensity depending on individual (figure 2d).

Description. Male (from live material, n=10). Head. Front tan, with about 10 short setulae. Frontal length 0.34 (0.33–0.34) mm; frontal index = 0.95 (0.90–1.02), top to bottom width ratio = 1.32 (1.24–1.43). Ocellar triangle slightly raised, pollinose gray. Frontal vittae broad and dark brown. Medial frontal vittae a light central stripe from ocellar triangle to anterior edge of frons. Orbital plates slightly broad on anterior part. A dark brown spot covers most of posterior part of orbital plate. The posterior orbital seta arises from a dark brown spot. Orbital setae black, or2 just outside of or1, or1/or3 ratio = 0.86 (79–94), or2/or1 ratio = 0.52 (0.46–0.63); ocellar/postocellar setae ratio= 1.54 (1.35–1.74), ocellar setae/frontal length ratio = 0.79 (0.74– 0.85) A dark spot exists immediately anterior to orbital plate. Further anteriad with row of 7–8 short black setulae on lateral margins. Vibrissa strong, vibrissal index = 0.55 (0.42–0.65). Face tan. Carina light brown with apical section clear, strongly sulcate, broader below (nose-like), and dorsally slightly grooved. Gena pale tan; the diameter of the eye about 6–7 times the width of the gena (Cheek index). Eye dark red, eye index = 1.14 (1.06–1.23). Occiput tan, brown above foramen. Pedicel tan and darker dorsally. Flagellomere tan and darkened basally. Arista with 3–4 dorsal, 2 ventral, and about 6 small inner branches, plus terminal fork. Proboscis tan-white, c1ypeus brownish. Palpus light brownish, with about 3–4 black setae along lower margin, apical one strongest.

Thorax ( Fig. 1 a): length 1.05 (0.96–1.11) mm. Mesonotum with pale brown pollinose ground color and darker brown spots at base of setulae often fused into irregular patterns. Spots occasionally enlarged at base of dorsocentral, posterior alars and scutellar setae. Six rows of acrostichal setulae. No prescutellars. Postpronotal or humeral (h) index = 1.18 (1.14–1.28). Dorsocentral (dc) index = 0.67 (0.63–0.72). Disk of scutellum gray with a noticeably darker “u” shaped mark. Basal setae slightly convergent, apical scutellar convergent; scut index = 0.90 (0.86–0.92). Pleura darkened along dorsal region, sterno index = 0.77 (0.72–0.81), medial katepisternal seta minute. Haltere tan-yellow, a brownish spot on upper side of knob and second section of pedicel. Legs tan with darker banding on all three tibiae and distally on 2nd and 3rd femora, preapical setae on all tibiae, apical seta on fore and mesotibia.

Wing: Hyaline, apex of the sub-costal break darkened (as in D. longicornis ) with two developed setae; dorsal seta slightly shorter and stronger than ventral seta. Third costal section with heavier setae on basal 2/5. Crossvein dM-Cu slightly shadowed (clouded, as in D. longicornis ), crossvein R-M slight broad and clouded but less than dM-Cu, also a small clouded area on R1 distal margin. Length 1.88 (1.79–2.00) mm, length to width ratio = 1.94 (1.88–2.00). Indices: Costa (C index) = 2.51 (2.38–3.65), C-III/C-IV (ac index) = 2.57 (2.47–2.80), C-III/M-III (4C index) = 1.02 (0.95–1.09), M-IV/M-III (4v index) = 1.80 (1.67–1.91), CuA (apical section)/dM-Cu (5x index)= 1.44 (1.31–1.60), CuA (apical section)/M-III (M index) = 0.58 (0.51–0.65), Basal R4+5/M-III (prox. X index) = 0.60 (0.56–0.71).

Abdomen ( Fig. 2 a, b): Pale yellow, each tergite with a broad dark brown posterior band interrupted at mid dorsal line. Band continues anteriorly on upper lateral edge of 2nd, 3rd, and 4th tergites, usually expanding at border of preceding segment. Lower lateral margin of the tergites with a narrow elongate brown bar, rarely continuous with its respective band. By contrast the bands of segments 5 and 6 are continuous to lower lateral margin. Color of 5th segment occasionally diluted out in mid lateral area.

External genitalia ( Fig. 3 a). Surstylus with 9–11 prensisetae and 8 marginal bristles, 3 or 4 of which are present on upper surface. Mediodorsal lobe of epandrium enlarged and bare, without setae, to form a rounded toe that overlaps surstylus laterally. Cerci fused to lower ½. Apex of each cercus with a cluster of 6–7 setae. Distiphallus with numerous small scales and a dorsally directed short finch-like beak flanked immediately below by smaller ones (very similar to D. huckinsi ). Dorsal cleft elongate, as long as aedeagus. Paraphysis club-shaped with one sensillum. Phallosomal index=2.0 (1.7–2.1). Phallosomal length 0.32 mm.

Internal characters of imagines. Testes lemon yellow with 2 inner and 3 outer coils. Ventral receptacle elongated with about 6–7 loose coils. Spermathecae very small, spherical with chitinized structure surrounded by an outer membrane.

Female. It fit male description except as follow: abdomen similar to male except lateral light area on the tergites 2, 3 and 4 larger; also, color of remaining two segments often diluted out in mid-lateral area. Measurements (from live material, n=10).Wing length 2.34 (2.23–2.42) mm, length to width ratio = 1.95 (1.81–2.08). Indices: Costa = 2.78 (2.52–3.00), C-III/C-IV = 2.43 (2.10–2.88), C-III/M-III = 0.92 (0.84–1.00), M-IV/M-III = 1.80 (1.73–1.89), CuA (apical section)/dM-Cu = 1.27 (1.10–1.37), CuA (apical section)/M-III = 0.53 (0.46– 0.56), Basal R4+5/M-III = 0.68 (0.62–0.73).

Immature Stages. Eggs measure 0.4–0.6mm (n=30) with 4 slender filaments. Posterior filaments average 30% (28–36%) longer than egg. Anterior filaments slightly shorter. Puparia tan to light brown. Horns very long. Horn index from the grand mean of separate measurements of pupal length and horn length from both cultures 1.33 (n=117). The light gray anterior spiracles are 24–30% of the horn length and consist of 12 long and about 8 shorter branches. Stalk of horns turn black when exposed, the spiracles do not. Table 1 shows an analysis of horn and pupal length of 11 species including two strains of D. sonorae .

Chromosomes. Metaphase plate (A659 from Alamos, Sonora) shows five pairs of rods and one pair of dots. The X chromosome is larger than the autosomes, the Y is 1/3 to ½ length of X. Polytene chromosomes show little or no chromocenter but there is heterochromatin at the base of the X. According to Wasserman (1992), this species is homosequential with D. longicornis except for a single fixed inversion (2k6) on the second chromosome.

Type Material. HOLOTYPE male, 10 males and 10 females TYPE SERIES from laboratory culture from Alamos, Sonora, Mexico, collected by William B. Heed in March, 1985 are deposited at the National Drosophila Stock Center collection at the University of Arizona in Tucson, Arizona. PARATYPES 8 males and 5 females from Alamos, Sonora, Mexico, collected by William B. Heed in March, 1985 and PARATYPES 7 males and 5 females from Los Hornos, Sinaloa, Mexico, collected by William B. Heed in November 1984 are deposited at the Smithsonian Diptera collection ( USNM) in Washington D.C. A live D. sonorae culture (catalog number 15081–1312.00 from Alamos, Sonora); and two preserved stocks (15081–1312.01 from Los Hornos, Sinaloa and 15081–1312.02 from Navojoa , Sonora), are available at the National Drosophila Stock Center.

Etymology: This species is named for the state of Sonora, located in northwestern Mexico along the bor- der with Arizona.

Distribution and Ecology. Drosophila sonorae has been reared from various species of flat-leafed Opuntia from four separate localities in southern Sonora and northern Sinaloa, Mexico ( Table 2 ). They are Navojoa , Sonora, and El Dorado, Sinaloa, at lower elevations in coastal thorn forests while Alamos, Sonora, and Los Hornos, Sinaloa, are at somewhat higher in elevation in the tropical deciduous forest as outlined by Leopold (1959).

Place & North date Opuntia species & Drosophila Drosophila Drosophila Drosophila Drosophila

latitude pads used aldrichi navojoa longicornis arizonae sonorae Of the five species and 5,686 flies presented in Table 2 , D. sonorae represents only 5% of the total, even though the rearing records were collated on the basis of the presence of this species. An explanation for the low numbers may be found in Richardson (1982) who reported the time to emergence was almost twice as long between D. propachuca and its two sibling species D. longicornis and D. pachuca . Perhaps D. sonorae also has extended egg to adult development time.

Drosophila longicornis and D. arizonae Ruiz, Heed & Wasserman 1990 , are much more common in other parts of Mexico and southwestern United States than tabulated in the table, while D. aldrichi Patterson 1940 , and D. navojoa Ruiz, Heed & Wasserman 1990 , are more common at these localities. A portion of the data was presented previously by Ruiz and Heed (1988).

Test Crosses. All attempts to produce hybrids between D. sonorae and D. longicornis failed, even utilizing ~ 330 females and ~ 330 males in various combinations of mass matings in bottles and between 5 to 20 flies of each sex in small vials.

In particular, D. sonorae from Los Hornos (Heed’s collection A877) produced no offspring in reciprocal matings with D. longicornis from Navojoa (A893). Also, D. longicornis from Santa Maria de la Regla, Hidalgo (A961), did not hybridize with D. sonorae from Los Hornos. D. sonorae from Alamos (A892) was crossed reciprocally with D. longicornis from Navojoa , which also produced no progeny. All tests were negative even though eggs were present in most of the vials and bottles. The only successful crosses that produced progeny were D. longicornis from Navojoa with D. longicornis from Santa María de la Regla and D. sonorae from Alamos with D. sonorae from Los Hornos.

Finally, D. propachuca (A 961 B) from Santa Maria de la Regla, Hidalgo and D. spenceri from Playa Azul, Michoacán (A 1010) failed to produce hybrids with D. sonorae from Alamos although they were quite fertile as controls.

Figures

FIGURE 1. Drosophila sonorae: a) dorsal view male thorax; b) pupal horns, one of the largest in the genus Drosophila.

FIGURE 2. Male abdomen: dorsal (a) and lateral (b) view of Drosophila sonorae; dorsal (c) and lateral (d) view of Drosophila longicornis.

FIGURE 3. Male genitalia in the longicornis cluster: (a) D. sonorae external male genitalia. Lateral aspect of aedeagus (at scale): (b) D. sonorae, (c) D. huckinsi, and (d) D. huichole.

Tables

TABLE 2. Total numbers of flies reared from various species of fermenting Opuntia pads that included Drosophila sonorae sp. nov.

Navojoa , Sonora Oct-76 ficus-indica (18) 2,026 (27o 11’)	65	-	5	3 (0.1%)
Navojoa , Sonora Mar-85 wilcoxii (33) 467 (27o 11’)	239	21	6	62 (7.8%)
Alamos, Sonora Oct-76 Unknown sp. (6) - (27o 03’)	-	1	2	60 (95.2%)
Alamos, Sonora Mar-85 velutina complex 1,320 (27o 03’) (101)	7	121	1	40 (2.7%)
Los Hornos, Nov-84 wilcoxii (19) 59 Sinaloa (27o 05’)	-	-	-	116 (66.3%)
El Dorado, Nov-84 wilcoxii (19) 175 Sinaloa (27o 16’)	880	-	-	10 (0.9%)
Total 4,047	1,191	143	14	291